A Confederate submarine crew may have torpedoed themselves, dying from shock waves from the very blast they used to sink a Union ship. In 1864, rebel sailors apparently didn’t know you want be far away when your torpedoes explode, researchers surmised.

A new study published Wednesday in the journal Nature said the submarine H.L. Hunley won the distinction of being the first combat submarine to sink an enemy ship when it smacked a 135-pound torpedo filled with black powder into the USS Housatonic in Charleston Harbor, at close range.

The Hunley's eight-man crew perished and a long mystery of what happened to the submarine began.

Nature said the skeletons of the crew were found when the submarine was raised in 2000, after being discovered in 1995.

"The pressure wave from the explosion was transmitted into the submarine," said Rachel Lance, a graduate student in injury biomechanics at Duke University and lead author of the study, per Nature. "It was sufficiently large …"

One of the prevailing theories about what happened to the Hunley had been that the crew of the Housatonic managed to shoot bullet holes in the submarine, another was that it collided with a ship in the area.

However, when the submarine was raised, there was no obvious damage to its hull, CNN reported. The crew had suffered no broken bones and there was no sign they tried to escape.

"For the Hunley, since the hull was exposed from all radial directions simultaneously and accompanied by motion of the ship itself, there may be no clear direction of motion even if the pressure wave did translate the crewmen," the study said. "Lethal pulmonary blast injuries are therefore consistent with the lack of skeletal trauma and the positions of the crew at their battle stations."

To test her theory, Lance, an engineer at the Naval Surface Warfare Center, set off test explosions near a model of the submarine in a North Carolina pond. There were pressure gauges inside the model.

Lance told CNN she was able to determine from the experiments' calculations that a shock wave from the torpedo blast would have instantly killed those aboard the Hunley.

"Any explosive we've seen in the field ... would definitely create a lethal wave," Lance said. "These types of injuries are not subtle. The damage is immediate."